Solid-state image pickup device and radiation image pickup device

ABSTRACT

A solid-state image pickup device according to the present invention has a plurality of photoelectric conversion elements and a plurality of switching elements, characterized in that the photoelectric conversion element is formed above at least one switching element, and a shielding electrode layer is disposed between the switching elements and the photoelectric conversion elements. Further, a radiation image pickup device according to the present invention has a radiation conversion layer for directly converting radiation into electric charges, and a plurality of switching elements, and is characterized in that the radiation conversion layer is formed above one or more switching elements, and a shielding electrode layer is disposed between the switching elements and the radiation conversion layer.

TECHNICAL FIELD

The present invention relates in general to a radiation image pickupdevice for detecting radiation such as X-rays, alpha rays, beta rays, orgamma rays, the device being applied to a medical image diagnosissystem, a non-destructive inspection system, an analyzer or the like.More particularly, the invention relates to a solid-state image pickupdevice for use in a flat panel detector (hereinafter referred to as “anFPD” for short when applicable). The FPD is obtained by combining asensor array constituted by a sensor device using non-monocrystallinesilicon, e.g., amorphous silicon (hereinafter referred to as “a-Si” forshort) and TFT elements, with a phosphor for converting radiation intovisible rays of light, etc.

BACKGROUND ART

In recent years, the technique for TFTs for liquid crystal displaydevices has progressed, and servicing for information infrastructure hasbeen made satisfactory. Thus, at the present time, the FPD is proposed,and even in the medical image field, the FPD can have a large area anddigitization of the FPD is attained.

This FPD is adapted to read out a radiation image in an instant todisplay the radiation image thus read out on a display devicesimultaneously, and an image can be directly fetched in the form ofdigital information from the FPD. Thus, the FPD has the feature thathandling management is convenient in safekeeping of data, or process andtransfer of data. In addition, it was verified that though thecharacteristics such as sensitivity depend on photographing conditions,the characteristics are equal to or superior to those in a conventionalscreen film photographing method or a computed radiography photographingmethod.

Commercialization of the FPD has been attained. On the other hand,various proposals for the FPD have been made for the purpose of aimingat further enhancing the sensitivity. For example, in a report made in aliterature of L. E Antonuk et al.: “SPIE Medical Imaging VI”, February,pp. 23 to 27, 1992, there is disclosed a structure in which a sensorelement is formed on a TFT element. In this related art example,adoption of the above-mentioned structure allows an open area ratio ofthe sensor element to be increased to make enhancement of sensitivitypossible. In addition, it is described that since the TFT element isdisposed right under the sensor element, an unnecessary parasiticcapacity is formed, and hence a grounded plane is disposed.

In addition, in a proposal made in a literature of the specification inU.S. Pat. No. 5,498,880 granted to DuPont, likewise, there is shown astructure in which in order to increase an open area ratio, a sensorelement is formed on a TFT element. In this related art example, thereis adopted the structure in which an electrode connected to asource/drain electrode of the TFT covers the TFT element, and alsobecomes a separate electrode of the sensor element.

On the other hand, in a proposal as well in a literature of JapanesePatent Application Laid-Open No. 2000-156522 filed by Canon KabushikiKaisha, there is shown a structure in which for the purpose of aiming atincreasing an open area ratio, a sensor element is formed above a TFTelement. In this related art example, there is adopted the structure inwhich the sensor element is formed over the TFT element through aninterlayer film.

However, in the above-mentioned FPD having the structure in which thesensor element is formed on the TFT element, the separate electrode ofthe sensor element acts as a back gate electrode of the TFT element.Hence, a problem such as generation of a leakage current of the TFTelement is caused due to the fluctuation in electric potential of theseparate electrode. Such a problem appears in the form of degradation ofquality of an image.

In a case where for example, an area having a large sensor outputsignal, and an area having a small sensor output signal are disposedadjacent to each other, such crosstalk as to blur a boundary betweenthese areas appears. In addition, there is caused a problem that asensor saturation output is decreased to reduce a dynamic range.

DISCLOSURE OF THE INVENTION

The present invention has been made in the light of the foregoingproblems, and it is, therefore, an object of the present invention tomake it possible that even when an electric potential of a separateelectrode of a sensor element disposed above a switching elementfluctuates, the fluctuation in characteristics due to generation of aleakage current of the switching element is suppressed to attainenhancement of sensitivity.

In order to solve the above-mentioned problems, according to the presentinvention, there is provided a solid-state image pickup device includinga plurality of photoelectric conversion elements and a plurality ofswitching elements, characterized in that the photoelectric conversionelement is formed above at least one switching element, and a shieldingelectrode layer is disposed between the switching elements and thephotoelectric conversion elements.

Further, according to the present invention, there is provided aradiation image pickup device including a radiation conversion layer fordirectly converting radiation into electric charges, and a plurality ofswitching elements, characterized in that the radiation conversion layeris formed above one or more switching elements, and a shieldingelectrode layer is disposed between the switching elements and theradiation conversion layer.

According to the present invention, the shielding layer is provided soas to be interposed between the switching element and the sensor portionformed above the switching element, whereby even when an electricpotential of a separate electrode of the sensor element disposed abovethe switching element fluctuates, the fluctuation in characteristics dueto generation of a leakage current of the switching element can besuppressed to attain enhancement of sensitivity.

Other features and advantages of the present invention will be apparentfrom the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1 is a schematic equivalent circuit diagram of pixels disposed inmatrix of 3×3 of a solid-state image pickup device according toEmbodiment 1 of the present invention;

FIG. 2 is a schematic plan view of one pixel of the solid-state imagepickup device according to Embodiment 1 of the present invention;

FIG. 3 is a schematic plan view of four pixels of the solid-state imagepickup device according to Embodiment 1 of the present invention;

FIG. 4 is a schematic cross sectional view of the solid-state imagepickup device according to Embodiment 1 of the present invention;

FIG. 5 is a schematic equivalent circuit diagram of pixels disposed inmatrix of 3×3 of a solid-state image pickup device according toEmbodiment 2 of the present invention;

FIG. 6 is a schematic plan view of one pixel of the solid-state imagepickup device according to Embodiment 2 of the present invention;

FIG. 7 is a schematic plan view of four pixels of the solid-state imagepickup device according to Embodiment 2 of the present invention;

FIG. 8 is a schematic cross sectional view of the solid-state imagepickup device according to Embodiment 2 of the present invention;

FIG. 9 is a schematic equivalent circuit diagram of pixels disposed inmatrix of 3×3 of a solid-state image pickup device according toEmbodiment 3 of the present invention;

FIG. 10 is a schematic plan view of one pixel of the solid-state imagepickup device according to Embodiment 3 of the present invention;

FIG. 11 is a schematic plan view of four pixels of the solid-state imagepickup device according to Embodiment 3 of the present invention;

FIG. 12 is a schematic cross sectional view of the solid-state imagepickup device according to Embodiment 3 of the present invention; and

FIG. 13 is a schematic cross sectional view of a radiation image pickupdevice according to Embodiment 4 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, embodiments of the present invention will hereinafter be describedwith reference to the accompanying drawings.

Embodiment 1

Description will hereinafter be given with respect to a solid-stateimage pickup device using a MIS type photodiode (hereinafter referred toas “a PD” for short when applicable) according to Embodiment 1 of thepresent invention.

FIG. 1 is a schematic equivalent circuit diagram of pixels disposed inmatrix of 3×3 of a solid-state image pickup device according toEmbodiment 1, FIG. 2 is a schematic plan view of one pixel of thesolid-state image pickup device according to this embodiment, FIG. 3 isa schematic plan view of four pixels of the solid-state image pickupdevice according to this embodiment, and FIG. 4 is a schematic crosssectional view of the solid-state image pickup device according to thisembodiment.

In FIGS. 1 and 2, reference numeral 101 designates a MIS type PD as aphotoelectric conversion element (sensor element); reference numeral 102designates a transferring TFT as a switching element (thin filmtransistor); reference numeral 103 designates a transferring TFT drivingwiring; reference numeral 104 designates a signal line; referencenumeral 105 designates a sensor biasing wiring; reference numeral 106designates a shielding wiring (GND wiring); reference numeral 107, asource/drain electrode layer of the transferring TFT 102; referencenumeral 108, a contact hole; and 109, a sensor lower electrode layer.

In FIG. 4, reference numeral 110 designates an insulating substrate madeof glass or the like; reference numeral 111 designates a gate insulatingfilm made of SiN, SiO₂ or the like; reference numeral 112 designates afirst amorphous semiconductor layer made of a-Si or the like; referencenumeral 113 designates a first n⁺ type layer (ohmic contact layer);reference numerals 114 and 115 each designate an interlayer insulatingfilm made of SiN, SiO₂, Benzocyclobutene (BCB), Polyimide (PI) or thelike;

-   -   reference numeral 116 designates an insulating film made of SiN,        SiO₂ or the like; reference numeral 117, a second amorphous        semiconductor layer made of a-Si or the like; reference numeral        118, a second n⁺ type layer (hole blocking layer) made of        microcrystalline silicon, a-Si or the like; reference numeral        119, a transparent electrode layer made of ITO, SnO₂ or the        like; reference numeral 132, a passivation layer made of SiN, PI        or the like; reference numeral 134, an adhesion layer; and 135,        a phosphor layer acting as a wavelength conversion layer.

Note that, in FIG. 4, reference numerals 103, 105 and 106 designate agate electrode layer, a sensor biasing electrode layer, and a shieldingelectrode layer, respectively. The insulating film 116, the secondamorphous semiconductor layer 117 made of a-Si or the like, and thesecond n⁺ type layer 118 constitute a photoelectric conversion layer ofthe MIS type PD 101.

The gate electrode layer 103, the gate insulating film 111 made of SiN,SiO₂ or the like, the first amorphous semiconductor layer 112 made ofa-Si or the like, the first n⁺ type layer (ohmic contact layer) 113, andthe source/drain electrode layer 107 for the transferring TFT constitutethe transferring TFT 102. The photoelectric conversion layer is formedabove the transferring TFT 102, and hence the transferring TFT 102 iscovered with the photoelectric conversion layer.

The shielding electrode layer 106 is disposed so as to be interposedbetween the MIS type PD 101 and the transferring TFT 102.

Radiation such as X-rays is made incident from an upper side in thepaper of FIG. 2 to be converted into visible rays of light through thephosphor layer 135. The resultant rays are then converted into electriccharges by the MIS type PD 101 to be accumulated in the MIS type PD 101.Thereafter, the transferring TFT 102 is operated by a TFT drivingcircuit through the transferring TFT driving wiring 103 to transferthese accumulated electric charges to the signal line 104 connected toone of the source electrode and the drain electrode of the transferringTFT 102 to be processed in the signal processing circuit, and theresultant analog signal is then subjected to A/D conversion in the A/Dconversion circuit to be outputted. At this time, an electric potentialof the shielding wiring 106 is fixed to a constant electric potentialsuch as GND at all times.

In this embodiment, the shielding wiring 106 disposed below the sensorelement is grounded. As a result, even if an electric potential of aseparate electrode of the sensor element fluctuates, the fluctuation incharacteristics due to generation of a leakage current of the TFTelement can be suppressed to allow enhancement of sensitivity to beattained. In addition, since the shielding wiring 106 does not overlapthe signal line 104 at all, no parasitic capacity is formed between theshielding wiring 106 and the signal line 104, and hence degradation ofthe sensor sensitivity can also be suppressed.

In this embodiment, there has been shown the specific case where a widthof the shielding wiring 106 is identical to a channel width of the TFT.However, in order to reduce a capacity in a cross portion between thetransferring TFT driving wiring 103 and the shielding wiring 106, it isalso possible to use a wiring having a width smaller than the channelwidth in the cross portion between the transferring TFT driving wiring103 and the shielding wiring 106.

In addition, the shielding wiring 106 has only to be held at a constantelectric potential, and hence it is also possible to set the electricpotential of the shielding wiring 106 to any constant electric potentialother than GND. Since a resistance of the shielding wiring 106 may behigh, a wiring made of a high melting point metal such as molybdenum(Mo), chromium (Cr), titanium (Ti), tungsten (W), or molybdenum-tungsten(MoW) can be used as the shielding wiring 106. As a result, a limitationto a manufacturing process can be reduced. Moreover, of the layerincluding the gate electrode, the layer including the source/drainelectrode, the layer including the shielding electrode, and the layerincluding the sensor biasing electrode, the shielding electrode layer isformed as the thinnest wiring to reduce a difference in level and toreduce a difference in level of the sensor portion formed above theshielding wiring 106, resulting in improving the yield. This is becausean electrical resistance value of the shielding electrode layer may belarger than that of each of other electrode layers.

Embodiment 2

Description will hereinafter be given with respect to a solid-stateimage pickup device using a MIS type PD according to Embodiment 2 of thepresent invention.

FIG. 5 is a schematic equivalent circuit diagram of pixels disposed inmatrix of 3×3 of a solid-state image pickup device according toEmbodiment 2, FIG. 6 is a schematic plan view of one pixel of thesolid-state image pickup device according to this embodiment, FIG. 7 isa schematic plan view of four pixels of the solid-state image pickupdevice according to this embodiment, and FIG. 8 is a schematic crosssectional view of the solid-state image pickup device according to thisembodiment.

The same reference numerals as those in Embodiment 1 indicate the samecomponents.

In FIGS. 5 and 6, reference numeral 101 designates a MIS type PD;reference numeral 102 designates a transferring TFT; reference numeral103 designates a transferring TFT driving wiring; reference numeral 104designates a signal line; reference numeral 105 designates a sensorbiasing wiring; reference numeral 106 designates a shielding wiring (GNDwiring); reference numeral 108, a contact hole; reference numeral 109, asensor lower electrode layer; reference numeral 120, a resetting TFT asa switching element; reference numeral 121, a resetting TFT drivingwiring; and 126, a reset wiring.

In FIG. 8, reference numeral 110 designates an insulating substrate madeof glass or the like; reference numeral 111 designates a gate insulatingfilm made of SiN, SiO₂ or the like; reference numeral 112 designates afirst amorphous semiconductor layer made of a-Si or the like; referencenumeral 113 designates a first n⁺ type layer (ohmic contact layer);reference numerals 114 and 115 each designate an interlayer insulatingfilm made of SiN, SiO₂, Benzocyclobutene (BCB), Polyimide (PI) or thelike; reference numeral 116 designates an insulating film made of SiN,SiO₂ or the like; reference numeral 117, a second amorphoussemiconductor layer made of a-Si or the like; reference numeral 118, asecond n+ type layer (hole blocking layer) made of microcrystallinesilicon, a-Si or the like; reference numeral 119, a transparentelectrode layer made of ITO, SnO₂ or the like; reference numeral 107, asource/drain electrode layer of the transferring TFT 102; referencenumeral 122, a source/drain electrode layer of the resetting TFT;reference numeral 132, a passivation layer made of SiN, PI or the like;reference numeral 134, an adhesion layer; and 135, a phosphor layer.

Note that, in FIG. 8, reference numerals 103 and 121 each designate agate electrode layer, reference numeral 105 designates a sensor biasingelectrode layer, and reference numeral 106 designates a shieldingelectrode layer.

The insulating film 116, the second amorphous semiconductor layer 117made of a-Si or the like, and the second n⁺ type layer 118 constitute aphotoelectric conversion layer of the MIS type PD 101. The gateelectrode layer 103, the gate insulating film 111 made of SiN, SiO₂ orthe like, the first amorphous semiconductor layer 112 made of a-Si orthe like, the first n⁺ type layer (ohmic contact layer) 113, and thesource/drain electrode layer 107 for the transferring TFT constitute thetransferring TFT 102. The gate electrode layer 121, the gate insulatingfilm 111 made of SiN, SiO₂ or the like, the first amorphoussemiconductor layer 112 made of a-Si or the like, the first n⁺ typelayer (ohmic contact layer) 113, and the source/drain electrode layer122 of the resetting TFT constitute the resetting TFT 120. Thephotoelectric conversion layer is formed above the transferring TFT 102and the resetting TFT 120, and hence both the TFTs are covered with thephotoelectric conversion layer.

The shielding electrode layer 106 is disposed so as to be interposedbetween the MIS type PD 101 and the transferring TFT 102, and betweenthe MIS type PD 101 and the resetting TFT 120.

Radiation such as X-rays is made incident from an upper side in thepaper of FIG. 6 to be converted into visible rays of light through thephosphor layer 135. The resultant rays are then converted into electriccharges by the MIS type PD 101 to be accumulated in the MIS type PD 101.Thereafter, the transferring TFT 102 is operated by the transferring TFTdriving wiring 103 connected to a TFT driving circuit to transfer theseaccumulated electric charges to the signal line 104 connected to one ofthe source electrode and the drain electrode of the transferring TFT 102to be processed in the signal processing circuit, and the resultantanalog signal is then subjected to A/D conversion in the A/D conversioncircuit to be outputted. Thereafter, the resetting TFT 120 is operatedby the resetting TFT driving wiring 121 connected to the signalprocessing circuit to reset the MIS type PD 101. At this time, anelectric potential of the shielding wiring 106 is fixed to a constantelectric potential such as GND at all times.

In this embodiment, the shielding wiring 106 disposed below the sensorelement is grounded. As a result, even if an electric potential of aseparate electrode of the sensor element fluctuates, the fluctuation incharacteristics due to generation of a leakage current of the TFTelement can be suppressed to allow enhancement of sensitivity to beattained. In addition, since the shielding wiring 106 does not overlapthe signal line 104 at all, no parasitic capacity is formed between theshielding wiring 106 and the signal line 104, and hence degradation ofthe sensor sensitivity can also be suppressed.

In this embodiment, there has been shown the specific case where a widthof the shielding wiring 106 is identical to a channel width of the TFT.However, in order to reduce a capacity in a cross portion between therespective TFT driving wirings, it is also possible to use a wiringhaving a width smaller than the channel width in the cross portionbetween the respective TFT driving wirings.

Embodiment 3

Description will hereinafter be given with respect to a solid-stateimage pickup device using a MIS type PD according to Embodiment 3 of thepresent invention.

FIG. 9 is a schematic equivalent circuit diagram of pixels disposed inmatrix of 3×3 of a solid-state image pickup device according toEmbodiment 3, FIG. 10 is a schematic plan view of one pixel of thesolid-state image pickup device according to this embodiment, FIG. 11 isa schematic plan view of four pixels of the solid-state image pickupdevice according to this embodiment, and FIG. 12 is a schematic crosssectional view of the solid-state image pickup device according to thisembodiment.

The same reference numerals as those in Embodiment 1 indicate the samecomponents.

In FIGS. 9 and 10, reference numeral 101 designates a MIS type PD;reference numeral 104 designates a signal line; reference numeral 105designates a sensor biasing wiring; reference numeral 106 designates ashielding wiring (GND wiring); reference numeral 108 designates acontact hole; reference numeral 109 designates a sensor lower electrode;reference numeral 120 designates a resetting TFT; reference numeral 121designates a resetting TFT driving wiring; reference numeral 123, astorage capacitor; reference numerals 124 and 125 designate a switchingTFT and a reading TFT forming a source follower (SFA), respectively;reference numeral 126, a reset wiring; reference numeral 127, a contacthole through which the storage capacitor 123 and the shielding wiring106 are connected to each other; reference numeral 128, a switching TFTdriving wiring; and 130, a reading TFT driving electrode.

FIG. 12 is a schematic cross sectional view showing a part of thesolid-state image pickup device indicated by an arrow in FIG. 10.Reference numeral 110 designates an insulating substrate made of glassor the like; reference numeral 111 designates a gate insulating filmmade of SiN, SiO₂ or the like; reference numeral 112 designates a firstamorphous semiconductor layer made of a-Si or the like; referencenumeral 113 designates a first n⁺ type layer (ohmic contact layer);reference numerals 114 and 115 each designate an interlayer insulatingfilm made of SiN, SiO₂, Benzocyclobutene (BCB), Polyimide (PI) or thelike; reference numeral 116 designates an insulating film made of SiN,SiO₂ or the like; reference numeral 117, a second amorphoussemiconductor layer made of a-Si or the like; reference numeral 118, asecond n⁺ type layer (hole blocking layer) made of microcrystallinesilicon, a-Si or the like; reference numeral 119, a transparentelectrode layer made of ITO, SnO₂ or the like; reference numeral 122, asource/drain electrode layer of the resetting TFT; reference numeral129, a source/drain electrode layer of the switching TFT; referencenumeral 131, a source/drain electrode layer of the reading TFT;reference numeral 132, a passivation layer made of SiN, PI or the like;reference numeral 133, a contact hole; reference numeral 134, anadhesion layer; and 135, a phosphor layer.

Note that, in FIG. 12, reference numerals 121, 128, and 130 eachdesignate a gate electrode layer, reference numeral 105 designates asensor biasing electrode layer, and reference numeral 106 designates ashielding electrode layer.

The insulating film 116, the second amorphous semiconductor layer 117,and the second n⁺ type layer 118 constitute a photoelectric conversionlayer of the MIS type PD 101. The gate electrode layer 121, the gateinsulating film 111 made of SiN, SiO₂ or the like, the first amorphoussemiconductor layer 112 made of a-Si or the like, the first n⁺ typelayer (ohmic contact layer) 113, and the source/drain electrode layer122 for the resetting TFT constitute the resetting TFT 120. The gateelectrode layer 128, the gate insulating film 111 made of SiN, SiO₂ orthe like, the first amorphous semiconductor layer 112 made of a-Si orthe like, the first n⁺ type layer (ohmic contact layer) 113, and thesource/drain electrode layer 129 of the switching TFT constitute theswitching TFT 124. The photoelectric conversion layer is formed abovethe resetting TFT 120 and the switching TFT 124, and hence both the TFTsare covered with the photoelectric conversion layer.

The shielding electrode layer 106 is disposed so as to be interposedbetween the MIS type PD 101 and the resetting TFT 120, and between theMIS type PD 101 and the switching TFT 124.

Radiation such as X-rays is made incident from an upper side in thepaper of FIG. 10 to be converted into visible rays of light through thephosphor layer 135. The resultant rays are then converted into electriccharges by the MIS type PD 101 to be accumulated in the storagecapacitor 123 through the contact holes 108 and 133. Fluctuation inelectric potential corresponding to these accumulated electric chargesis caused in the gate electrode of the reading TFT 125. Thereafter, theswitching TFT 124 is operated through the switching TFT driving wiring128 so that the accumulated electric charges are read out through thesignal line 104 connected to one of the source electrode and the drainelectrode of the reading TFT 125 to be processed in the signalprocessing circuit. The resultant analog signal is then subjected to A/Dconversion in an A/D conversion circuit to be outputted. Thereafter, theresetting TFT 120 is operated through the resetting TFT driving wiring121 connected to the signal processing circuit to reset the storagecapacitor 123. At this time, an electric potential of the shieldingwiring 106 is fixed to a constant electric potential such as GND at alltimes.

In this embodiment, the shielding wiring 106 disposed below the sensorelement is grounded. As a result, even if an electric potential of aseparate electrode of the sensor element fluctuates, the fluctuation incharacteristics due to generation of a leakage current of the TFTelement can be suppressed to allow enhancement of sensitivity to beattained. In addition, since the shielding wiring 106 does not overlapthe signal line 104 at all, no parasitic capacity is formed between theshielding wiring 106 and the signal line 104, and hence degradation ofthe sensor sensitivity can also be suppressed.

In this embodiment, there has been shown the specific case where theshielding wiring portion is disposed above the two TFT portions and thestorage capacitor portion. However, it is also possible to dispose theshielding wiring portion above three TFT portions and the storagecapacitor portion.

In each of the embodiments 1 to 3 of the present invention describedabove, there has been shown the specific case where in the indirect typesolid-state image pickup device, the MIS type PD is used as thephotoelectric conversion element. However, it is also possible to use aPIN type PD. In case of the PIN type PD, the photoelectric conversionlayer includes a p⁺ type layer, a second amorphous semiconductor layer,and a second n⁺ type layer instead of the insulating film 116, thesecond amorphous semiconductor layer 117, and the second n⁺ type layer118, respectively.

Embodiment 4

Description will hereinafter be given with respect to a direct typeradiation image pickup device according to Embodiment 4 of the presentinvention.

FIG. 13 is a schematic cross sectional view of a direct type radiationimage pickup device. Reference numeral 110 designates an insulatingsubstrate made of glass or the like; reference numeral 111 designates agate insulating film made of SiN, SiO₂ or the like; reference numeral112 designates a first amorphous semiconductor layer made of a-Si or thelike; reference numeral 113 designates an n⁺ type layer (ohmic contactlayer); reference numerals 114 and 115 each designate an interlayerinsulating film made of SiN, SiO₂, Benzocyclobutene (BCB), Polyimide(PI) or the like; reference numeral 120 designates a resetting TFT;reference numeral 123 designates a storage capacitor; reference numerals124 and 125 designate a switching TFT and a reading TFT forming a sourcefollower (SFA), respectively; reference numeral 121 designates aresetting TFT driving wiring; reference numeral 122, a source/drainelectrode layer of the resetting TFT; reference numeral 129, asource/drain electrode layer of the switching TFT; reference numeral128, a switching TFT driving wiring; reference numeral 130, a readingTFT driving electrode; reference numeral 131, a source/drain electrodelayer of the reading TFT; reference numeral 132, a passivation layermade of SiN, PI or the like; reference numeral 133, a contact hole; andreference numeral 145, a radiation conversion layer for directlyconverting radiation into electric charges.

A circuit diagram of the radiation image pickup device shown in FIG. 13is the same as that of FIG. 1 except that the radiation conversion layer145 is used instead of the MIS type photodiode 101. In the direct typeradiation image pickup device, a-Se, GaAs, CdTe or the like is used as amaterial of the radiation conversion layer.

Note that, in FIG. 13, reference numerals 121, 128 and 130 eachdesignate a gate electrode layer, reference numeral 105 designates asensor biasing electrode layer, and reference numeral 106 designates ashielding electrode layer.

A layer structure of the resetting TFT 120 and the reading TFT 124 isthe same as that in Embodiment 3. The radiation conversion layer 145 isformed above the resetting TFT 120 and the reading TFT 124, and henceboth the TFTs 120 and 124 are covered with the radiation conversionlayer 145.

Further, the shielding electrode layer 106 is disposed so as to beinterposed between the radiation conversion layer 145 and the resettingTFT 120, and between the radiation-conversion layer 145 and theswitching TFT 124.

Radiation such as X-rays is made incident from an upper side of theradiation conversion layer shown in FIG. 13 to be directly convertedinto electric charges through the radiation conversion layer 145. Theresultant electric charges are then accumulated in the storage capacitor123 through the contact holes 108 and 133. Fluctuation in electricpotential corresponding to the accumulated electric charges is caused inthe gate electrode of the reading TFT 125. Thereafter, the switching TFT124 is operated through the switching driving wiring 128 so that theaccumulated electric charges are read out through the signal line 104connected to one of the source electrode and the drain electrode of thereading TFT 125 to be processed in a signal processing circuit. Theresultant analog signal is then subjected to A/D conversion in an A/Dconversion circuit to be outputted. Thereafter, the resetting TFT 120 isoperated through the resetting TFT driving wiring 121 connected to thesignal processing circuit to reset the storage capacitor 123. At thistime, an electric potential of the shielding wiring 106 is fixed to aconstant electric potential such as GND at all times.

While above, the embodiments of the present invention have beendescribed, preferred embodiment modes of the present invention will nowbe enumerated as follows.

Embodiment Mode 1

A solid-state image pickup device including a plurality of photoelectricconversion elements and a plurality of switching elements, characterizedin that the photoelectric conversion element is formed above at leastone switching element, and a shielding electrode layer is disposedbetween the switching elements and the photoelectric conversionelements.

Embodiment Mode 2

A solid-state image pickup device according to Embodiment Mode 1,characterized in that one photoelectric conversion element and one ormore switching elements are disposed in one pixel.

Embodiment Mode 3

A solid-state image pickup device according to Embodiment Mode 1 or 2,characterized in that the photoelectric conversion element has aphotoelectric conversion layer, and the photoelectric conversion layerincludes an insulating layer, a semiconductor layer, and a high impurityconcentrated semiconductor layer.

Embodiment Mode 4

A solid-state image pickup device according to embodiment Mode 1 or 2,characterized in that the photoelectric conversion element has aphotoelectric conversion layer, and the photoelectric conversion layerincludes a first high impurity concentrated semiconductor layer of oneconductivity type, a semiconductor layer, and a second high impurityconcentrated semiconductor layer of a conductivity type opposite to theone conductivity type of the first high impurity concentratedsemiconductor layer.

Embodiment Mode 5

A solid-state image pickup device according to any one of EmbodimentModes 1 to 4, characterized in that the shielding electrode layer is notformed above a signal line connected to one of a source electrode and adrain electrode of the switching element.

Embodiment Mode 6

A solid-state image pickup device according to any one of EmbodimentModes 1 to 5, characterized in that the shielding electrode layer isheld at a constant electric potential.

Embodiment Mode 7

A solid-state image pickup device according to Embodiment Mode 6,characterized in that the shielding electrode layer is grounded.

Embodiment Mode 8

A solid-state image pickup device according to any one of EmbodimentModes 1 to 7, characterized in that each of the switching elements isconstituted by a TFT, and the shielding electrode layer is disposed soas to cover an upper portion of a channel of each of the TFTs.

Embodiment Mode 9

A solid-state image pickup device according to Embodiment Mode 8,characterized in that the shielding electrode layer has a width equal toor smaller than a channel width of the TFT and is disposed so as tocross a TFT driving wiring.

Embodiment Mode 10

A solid-state image pickup device according to any one of EmbodimentModes 1 to 9, characterized in that the shielding electrode layer ismade of a high melting point metal.

Embodiment Mode 11

A solid-state image pickup device according to Embodiment Mode 10,characterized in that the shielding electrode layer is made ofmolybdenum (Mo), chromium (Cr), titanium (Ti), tungsten (W), ormolybdenum-tungsten (MoW).

Embodiment Mode 12

A solid-state image pickup device according to Embodiment Mode 1,characterized in that the shielding electrode layer is an electrodelayer thinner than each of a gate electrode layer, a source/drainelectrode layer, and a sensor biasing electrode layer.

Embodiment Mode 13

A solid-state image pickup device according to Embodiment Mode 1,characterized in that the solid-state image pickup device includes agate electrode layer, a gate insulating layer, a first amorphoussemiconductor layer, a first n type semiconductor layer, a source/drainelectrode layer, a first interlayer insulating layer, the shieldingelectrode layer, a second interlayer insulating layer, a sensor lowerelectrode layer, an insulating layer, a second amorphous semiconductorlayer, a second n type semiconductor layer, a transparent electrodelayer, and a sensor biasing electrode layer.

Embodiment Mode 14

A solid-state image pickup device according to Embodiment Mode 13,characterized in that one photoelectric conversion element and one ormore TFTs are disposed in one pixel.

Embodiment Mode 15

A radiation image pickup device, characterized in that a wavelengthconversion unit is disposed above the photoelectric conversion elementin the solid-state image pickup device as described in any one ofEmbodiment Modes 1 to 9.

Embodiment Mode 16

A radiation image pickup device according to Embodiment Mode 15,characterized in that one photoelectric conversion element and one ormore switching elements are disposed in one pixel.

Embodiment Mode 17

A radiation image pickup device including a radiation conversion layerfor directly converting radiation into electric charges, and a pluralityof switching elements, characterized in that the radiation conversionlayer is formed above one or more switching elements, and a shieldingelectrode layer is disposed between the switching elements and theradiation conversion layer.

Embodiment Mode 18

A radiation image pickup device according to Embodiment Mode 17,characterized in that the radiation image pickup device includes a gateelectrode layer, a gate insulating layer, a first amorphoussemiconductor layer, a first n type semiconductor layer, a source/drainelectrode layer, a first interlayer insulating layer, the shieldingelectrode layer, a second interlayer insulating layer, a sensor lowerelectrode layer, a radiation conversion layer, and a sensor biasingelectrode layer.

As set forth hereinabove, according to the present invention, even iffluctuation in electric potential of the separate electrode of thesensor element is caused, the fluctuation in characteristics due togeneration of a leakage current of the switching element can besuppressed by provision of the shielding wiring disposed below thesensor element to allow enhancement of sensitivity to be attained.Moreover, since the shielding wiring does not overlap the signal line atall, a parasitic capacity formed between the shielding wiring and thesignal line can be reduced to allow the degradation as well of thesensor sensitivity to be suppressed.

In addition, the shielding wiring having the width smaller than thechannel width is used in the cross portion between the shielding wiringand the driving wiring of the switching element is used to allow thegate wiring capacity as well to be reduced.

As many apparently widely different embodiments of the present inventioncan be made without departing from the spirit and scope thereof, it isto be understood that the invention is not limited to the specificembodiments thereof except as defined in the claims.

1. A solid-state image pickup device comprising a plurality ofphotoelectric conversion elements and a plurality of switching elements,characterized in that each photoelectric conversion element is formedabove at least one switching element, and a shielding electrode layer isdisposed between the switching elements and the photoelectric conversionelements.
 2. A solid-state image pickup device according to claim 1,wherein one photoelectric conversion element and one or more switchingelements are disposed in one pixel.
 3. A solid-state image pickup deviceaccording to claim 1 or 2, wherein each photoelectric conversion elementhas a photoelectric conversion layer, and the photoelectric conversionlayer includes an insulating layer, a semiconductor layer, and a highimpurity concentrated semiconductor layer.
 4. A solid-state image pickupdevice according to claim 1 or 2, wherein each photoelectric conversionelement has a photoelectric conversion layer, and the photoelectricconversion layer includes a first high impurity concentratedsemiconductor layer of one conductivity type, a semiconductor layer, anda second high impurity concentrated semiconductor layer of aconductivity type opposite to the one conductivity type of the firsthigh impurity concentrated semiconductor layer.
 5. A solid-state imagepickup device according to any one of claims 1 to 2, wherein theshielding electrode layer is not formed above a signal line connected toone of a source electrode and a drain electrode of the switchingelement.
 6. A solid-state image pickup device according to any one ofclaims 1 to 2, wherein the shielding electrode layer is held at aconstant electric potential.
 7. A solid-state image pickup deviceaccording to claim 6, wherein the shielding electrode layer is grounded.8. A solid-state image pickup device according to any one of claims 1 to2, wherein each of the switching elements is constituted by a TFT, andthe shielding electrode layer is disposed so as to cover an upperportion of a channel of each of the TFTs.
 9. A solid-state image pickupdevice according to claim 8, wherein the shielding electrode layer has awidth equal to or smaller than a channel width of the TFT and isdisposed so as to cross a TFT driving wiring.
 10. A solid-state imagepickup device according to any one of claims 1 to 2, wherein theshielding electrode layer is made of a high melting point metal.
 11. Asolid-state image pickup device according to claim 10, wherein theshielding electrode layer is made of molybdenum (Mo), chromium (Cr),titanium (Ti), tungsten (W), or molybdenum-tungsten (MoW).
 12. Asolid-state image pickup device according to claim 1, wherein theshielding electrode layer is an electrode layer thinner than each of agate electrode layer, a source/drain electrode layer, and a sensorbiasing electrode layer.
 13. A solid-state image pickup device accordingto claim 1, wherein the solid-state image pickup device includes a gateelectrode layer, a gate insulating layer, a first amorphoussemiconductor layer, a first n type semiconductor layer, a source/drainelectrode layer, a first interlayer insulating layer, the shieldingelectrode layer, a second interlayer insulating layer, a sensor lowerelectrode layer, an insulating layer, a second amorphous semiconductorlayer, a second n type semiconductor layer, a transparent electrodelayer, and a sensor biasing electrode layer.
 14. A solid-state imagepickup device according to claim 13, wherein one photoelectricconversion element and one or more TFTs are disposed in one pixel.
 15. Aradiation image pickup device, characterized in that a wavelengthconversion unit is disposed above each photoelectric conversion elementin the solid-state image pickup device as claimed in any one of claims 1to
 2. 16. A radiation image pickup device according to claim 15, whereinone photoelectric conversion element and one or more switching elementsare disposed in one pixel.
 17. A radiation image pickup devicecomprising a radiation conversion layer for directly convertingradiation into electric charges, and a plurality of switching elements,characterized in that the radiation conversion layer is formed above oneor more switching elements, and a shielding electrode layer is disposedbetween the switching elements and the radiation conversion layer.
 18. Aradiation image pickup device according to claim 17, wherein theradiation image pickup device includes a gate electrode layer, a gateinsulating layer, a first amorphous semiconductor layer, a first n typesemiconductor layer, a source/drain electrode layer, a first interlayerinsulating layer, the shielding electrode layer, a second interlayerinsulating layer, a sensor lower electrode layer, a radiation conversionlayer, and a sensor biasing electrode layer.